1. Field of Invention
This invention relates to the transmission of data by the modulation of the light output of fluorescent and other arc lamps; including the visible or invisible light output of fluorescent lamps, neon lamps, mercury vapor lamps, high or low-pressure sodium lamps, or other high-intensity discharge lamps, or any metal-halide based lamps.
2. Description of Prior Art
Several methods for the transmission and reception of data messages exists. Many of these have application to offices, factories, and to buildings or complexes of buildings in general. For example, low-powered radio transmission can be used to transmit and receive data messages within a building, or the optical and infrared spectrum can be used for the transceiving of data.
However, the use of radio frequencies requires licensing and coordination for their use. Given the overcrowded radio spectrum in some areas, said licensing may be nearly impossible. In addition, while radio facilitates the transmission of data, in general that data transmission is limited in bandwidth and therefore limited in the speed of transmission. Additionally, radio energy is hard to confine, and there it is not practical to limit data transmission to the confines of any one building or office within a building or office.
In contrast, infrared transmission of data has the benefit of no licensing requirement, higher available bandwidth, and ease of confinement. However, as infrared energy is not transparent to walls or other structures, the cost of installation of an independent building-wide infrared-based transmission system is extreme. That is, each office and hallway within a building must be equipped with one or more infrared transmitters in order to provide coverage to the entire building. Each infrared transmitter will require lines for it's operating power and a data line for the data that is to be transmitted, thus requiring a supporting infrastructure that is both extensive and expensive.
In addition to wireless optical transmission as examined above, several examples exist of using modulated light in conjunction with optical fibers for the transmission of data, but these do not lend themselves to application to devices that are portable or mobile within buildings or offices.